In recent years, much emphasis has been placed on the benefits of regular exercise in maintaining physical well being and appearance. A steady proliferation of health clubs offering various sorts of exercising facilities and equipment has been evident, and numerous exercising devices for home use have been widely advertised and sold for those who lack the time, determination or facilities to engage in regular sports activities such as running, tennis, swimming or the like.
The need has long existed for a highly versatile, portable and inexpensive exercising device for home and personal use. Many home exercise devices currently available are of the assistive type wherein repetitive body motions are merely guided or helped. Yet authorities recognize that the benefits of most exercises can be significantly enhanced and performed with greater efficiency by employing resistive devices to place increased loads upon the muscles. Such resistive techniques are now widely used in modern weight training for athletes and in most supervised exercise programs.
Current studies also indicate that the most beneficial exercise results in many instances can be achieved with a limited number of quick repetitions using the maximum resistive force that the exerciser is capable of handling. Thus, as the exerciser gains strength, the resistance must be increased to maintain efficiency. For these purposes, adjustable weight lifting equipment is ideal, but most bar bell and dumb bell equipment is bulky, cumbersome and often even dangerous to use. More elaborate weight training machines are safe but even bulkier and in most instances too expensive to be within the means of many individuals to whom they are available only through health clubs, schools or other recreational facilities.
Although the adjustable twisted rope type of resistive exercisers enjoyed recent popularity as being less bulky and expensive, these did not permit rapid repetitions and could not be readily adapted to different exercises. Current cylinder type devices involving adjustable hydraulic, pneumatic and spring loaded resistance have similar practical limitations in use.
On the other hand, the well known chest expander devices achieve versatility with multiple springs detachably affixed between a pair of handles. With these expanders, the resistive force can be varied simply by changing the number of springs attached between the handles. However, the coil metal springs can pinch the skin or otherwise be extremely uncomfortable, even with a protective cover, if the springs are wrapped around or otherwise pressed against other body members. Also, the handles have to be securely held since, if one end slipped loose, the heavy handle and springs snapping back could injure the exerciser or those around him. Thus, as a practical matter, use of these expanders was for the most part confined to those few exercises wherein the handles could be firmly grasped in both hands with the springs away from the body.